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Section 7 — Fluid, Electrolyte & Nutrition Management Pending expert review v1.0 · July 2026 Baylor Ed. 33 cross-checked Sept 2026

Chapter 7.7 — Neonatal Nutrition & Growth: Requirements, Enteral/Parenteral Feeding, and Micronutrients

Board-review synthesis · pending expert review

Educational guideline — verify locally. Specific targets (energy/protein targets, glucose infusion rates, mineral/vitamin doses, monitoring thresholds) evolve and vary by gestation/state/guideline — verify against current authoritative references and local protocols. Cross-references: fluid/electrolyte (7.1/7.4), AKI (7.6), NEC/GI (Section 6), hypoglycaemia/IDM (endocrine).

1. Clinical Overview

Clinical Overview

The preterm infant must grow at an intrauterine rate — faster per kilogram than at any later time — while tolerating what is delivered, yet begins life with minimal reserves because most glycogen, fat, calcium, phosphorus, and iron are laid down in the third trimester it never had. Nutrition is the arithmetic of matching supply to this exceptional demand: adequate energy AND protein early (protein without enough energy is burned for fuel), human milk (fortified) as the reference feed for its NEC protection, cautious advancement of feeds in an immature gut, parenteral nutrition as a bridge to be dismantled, and deliberate micronutrient provision. Success is judged by growth itself — head circumference and growth velocity against the intrauterine standard — not by intake numbers alone.

2. Key Clinical Points

Key Clinical Points
  • Fetal growth is driven by insulin and IGFs (not growth hormone); glucose crosses the placenta by facilitated diffusion, amino acids by active transport.
  • Symmetric growth restriction = early insult (chromosomal/genetic, congenital infection); asymmetric (head-sparing) = later placental insufficiency. SGA (statistical) ≠ growth restriction (pathological).
  • Growth-restricted newborns are prone to hypoglycaemia, hypothermia, and polycythaemia (depleted stores + chronic hypoxia); IDM macrosomia carries post-natal hypoglycaemia from persistent hyperinsulinaemia.
  • Provide energy AND protein early: amino acids from the first day prevent catabolism; maintain an adequate protein:energy ratio or protein is burned for fuel. Feed (and measure) the brain first.
  • Human milk is the reference feed; its key preterm benefit is lower NEC risk. Donor human milk is preferred over formula when mother's own milk is unavailable.
  • Human milk must be fortified for the preterm (protein, calcium/phosphorus, energy); trophic feeds prime the gut early; safe oral feeding needs suck-swallow-breathe coordination (~mid-30s weeks).
  • Parenteral nutrition is a bridge to be dismantled; three complication families — metabolic, catheter-related (bloodstream infection, thrombosis), and hepatic (PNALD/cholestasis). Establishing enteral feeding is the single best treatment for PNALD.
  • Vitamin K is given to every newborn at birth to prevent vitamin K–dependent bleeding; breastfed infants need vitamin D, and preterm infants need earlier/greater iron.
  • Metabolic bone disease of prematurity: under-mineralised bones from inadequate calcium/phosphorus (missed 3rd-trimester accretion); heralded by rising alkaline phosphatase, may present with fractures from routine handling — prevent by fortification, vitamin D, and monitoring.
  • Zinc deficiency causes a peri-oral/perineal dermatitis with poor growth; copper/selenium deficiencies emerge on prolonged PN — include and monitor trace elements.

2+. Vitamins, Iron and Slow Growth on Enteral Feeds (Baylor Ed. 33)

Preterm infant fed (Baylor Table 14-12a)Daily supplementVitamin D goal
Human milk + human-milk-based fortifier, <2.5 kgIron 2–3 mg/kg + 1 mL multivitamin400 IU (800 IU with osteopenia or ALP >800, adding 1 mL vitamin D drops = 400 IU)
Human milk + bovine hydrolysed-protein liquid fortifierIron 2–3 mg/kg + vitamin D 200 IU if <2000 g400 IU (osteopenia: 400–600 IU as drops, goal 800)
Human milk + bovine liquid fortifier (the other brand)Vitamin D 200 IU if <1500 g400 IU (osteopenia: 400–600 IU as drops, goal 800)
Preterm formulaNone400 IU (osteopenia: add 1 mL vitamin D drops, goal 800)
Unfortified human milk<3.5 kg: iron 2 mg/kg + 1 mL multivitamin; ≥3.5 kg: 1 mL multivitamin with iron400 IU
Human milk + transitional formula (e.g., 5 breast-milk feeds + 3 formula feeds)<5 kg: iron 2 mg/kg + 1 mL multivitamin; >5 kg: 1 mL multivitamin with iron400 IU
Transitional formula<5 kg: 0.5 mL multivitamin ± iron (150 mL/kg/day already supplies ~2 mg/kg iron); >5 kg: none, individualize400 IU
Term formula, <3 kg0.5 mL multivitamin ± iron if taking <160 mL/kg/day400 IU
Rules behind the table
  • Breastfed infants under 2500 g at birth: start iron from the first week. Otherwise, start once full feeds are tolerated and the infant is at least 14 days old. Iron goal is 2–3 mg/kg/day below 1500 g, 2 mg/kg/day at 1500–2000 g, and 1–2 mg/kg/day at 2000–2500 g.
  • Term infants (Table 14-12b): breastfed with a stay under 1 week and AGA — vitamin D 400 IU/day (1 mL), and iron 1 mg/kg/day from 4 months (or iron-containing foods at 6 months). Breastfed with a stay over 1 week, many blood draws, or SGA — vitamin D plus iron 2 mg/kg/day. Mixed feeding — vitamin D 1 mL, iron 1–2 mg/kg according to formula intake. Term formula alone — usually nothing extra, but check vitamin D and iron intake against volume. Consider early iron after significant blood loss.
Slow growth on enteral feeds — a stepwise plan
  • Act when weekly gain is below 15 g/kg/day under 2000 g, or below 20 g/day over 2000 g. Change one thing at a time and allow 3–4 days between changes to judge the effect.
  • First, non-nutritional causes: feeding intolerance, acidosis, hyponatraemia, work of breathing, cold stress, anaemia, steroids, and infection including UTI.
  • Total-body sodium depletion — risk factors: unfortified donor milk, chronic diuretics, intestinal failure with a stoma; the serum sodium may be normal. Above 34 weeks PMA with poor growth and other causes excluded, a urine sodium below 30 mEq/L supports oral NaCl (low certainty, weak recommendation; strong in intestinal failure). Urine sodium cannot be read on diuretics, and below 34 weeks it does not correlate with growth — consider empirical extra sodium in high-risk infants instead.
  • Human-milk-fed preterm infants, in order:
    • Confirm the fortifier is actually added, and use bolus rather than continuous feeds (fat loss).
    • Raise fortified milk to 150, then about 160 mL/kg/day.
    • On human-milk fortifier at goal volume with protein met: add cream 2 kcal/oz, then 4 kcal/oz; then move to the +8 (28 kcal/oz) or +10 (30 kcal/oz) fortifier, making +10 from +8 at 1:1 if needed.
    • Give 1–4 feeds a day of 30 kcal/oz preterm formula alternating with fortified milk.
    • Use hind milk if supply allows (with lactation).
    • Take bovine fortifier above 24 kcal/oz only with the nutrition team, or add transitional formula powder, accepting the powder risk.
  • Formula-fed preterm infants, in order: exclude intolerance; confirm iron-fortified 24 kcal/oz preterm formula; advance to 150–160 mL/kg/day; if fluid is restricted, use 30 kcal/oz ready-to-feed, alone or mixed with 24 kcal/oz; single-nutrient modulars only as a last resort, with the dietitian.

3. References to Verify

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